PHYSIOLOGICAL EFFICIENCY OF ACIDS 
137 
show increasing effectiveness with the number of carbon atoms; 
for B-oxybutyric acid is about twice as active as oxypropionic 
acid. A comparison of oxybenzoic with benzoic acid showed 
that the latter is ten times as effective as the former. 
Perhaps, however, the influence of the constitution of the 
acid is most clearly demonstrated by a comparison of the effect 
of B-oxybutyric acid and oxyisobutyric acid. $-oxybutyric 
acid has more than four times the effect of oxyisobutyric acid. 
This is probably connected with the fact that while B-oxybutyric 
acid has the same carbon chain as butyric acid, oxyisobutyric 
acid has a branched carbon chain. 
Experiments upon di- or polybasic acids prove a trial of 
patience, as one cannot with certainty rely upon success. 
Whereas propionic, butyric, and valerianic acids cause mem- 
brane formation in all eggs of S. purpuratus practically without 
exception (provided that the concentration of acid and length 
of exposure are correctly chosen), the di- and polybasic organic 
acids do not affect the eggs of all females. Hence these acids 
behave like foreign blood sera, as regards membrane formation. 
This analogy indicates that the dibasic acids have a weaker 
effect than the monobasic acids, because they enter the egg 
more slowly. For obviously the degree of permeability of the 
egg differs in various females. In the next table I have put 
together results obtained from the eggs of an especially ‘“‘favor- 
able” female with oxalic, succinic, tartaric, and citric acids. 
TABLE XXII 
| | 7/500N | 7/500N 
.7/500 LUBY 4/500 
errr bedic acia| Sugcinie | Tartaric | ciiste Acid 
iL MT 2 ee ee 0 0 10% 0 
32 TAINS eae 15% 0 100 0 
2 20 Oop tse 10% 
AOTAMUTCS! Socios so 90 Orne el eee ence 60 
EOHTITMUGCS oss. hs et eo 90 DA SN aS ee Sere 80 
6 minutes ee aes eee 90 
